1. Field of the Invention
The present invention relates to an automobile door reinforcing member being arranged inside of an automobile door, so as to protect passengers in the vehicle by absorbing impact in the collision from a side face.
2. Description of the Related Art
A strict safety level for automobiles provides a built-in type of the automobile door reinforcing members, such as the side beam or the impact protection beam. For these automobile door reinforcing members, there are many proposals to achieve miniaturization, lightening, high strengthening on demand. For instance, these are shown in U.S. Pat. Nos. 5,580,120, 5,813,718, 5,820,202, 5,992,922 and U.S. Pat. No. 6,020,039 in the United States, furthermore, in Japanese Patent Application Laid-Open No. 216684/1996, No. 141368/1997, No. 215059/1995, No. 244456/1996, and No. 086172/1997.
The purpose of an automobile door reinforcing member is to protect passengers by absorbing impact in the collision from a side face. In order to achieve the purpose mentioned above, there are integral formed products such as formed by processing an original sheet or formed by transforming a pipe cross-section. By providing greater numbers of pipes and more complicated structures of pipe cross-section, the strength of products becomes higher. These are preferable structures as shown in U.S. Pat. No. 5,580,120, which is formed by one pipe but the sectional structure is complicated, U.S. Pat. Nos. 5,813,718, 5,820,202, Japanese Patent Application Laid-Open No. 244456/1996 and 086172/1997. In Japanese Patent Application Laid-Open No. 086172/1997, it indicates that, in particular, the necessity of high strengthened materials are required in the case of an one pipe structure.
Thus, in Japanese Patent Application Laid-Open No. 141368/1997 and No. 215059/1995 having only one pipe, improvement of strength is provided by welding. On the other hand, in U.S. Pat. No. 5,813,718, Japanese Patent Application Laid-Open No. 216684/1996, No. 244456/1996 and No. 086172/1997 made by annexed two pipes, a welding process is avoided to save accuracy after forming. Also, Japanese Patent Application Laid-Open No. 215059/1995 indicates that, in the case of avoiding the welding process, the rigidity is inferior when low strength materials are used. For this indication, however, there is a problem of sudden deterioration of strength by buckling even if high strength materials are used. Such sudden deterioration of strength is of great concern for providing sufficient safety for an actual collision from a side face.
From the above, the demands imposed on an automobile door reinforcing member are (1) miniaturizing and lightening of an reinforcing member in order to improve its installation space, (2) providing sufficient strength and rigidity when using low strength materials, and (3) preventing the occurrence of buckling.
Accordingly, the object of the present invention is to provide an automobile door reinforcing member consisting of twin pipes which shows sufficient strength and rigidity by a welding process with low strength materials being used.
The present invention is an automobile door reinforcing member consisting of the structure wherein a pair of pipes are formed from an original sheet material by: the joint surface being a middle portion of an original sheet in a width direction; the fold-back faces consist of the outer side faces of the pipes extending laterally from said joint surface, the outer wall faces extending from said outer side faces of the pipes, the inner side faces of the pipes extending from said outer wall faces, the inner wall faces extending from said fold-back faces to the joint surface, and the welding portions extending from said inner wall faces; forming these portions into lateral pipes by relatively bending the fold-back faces; folding boundary mark between the inner wall face and the welding portion into valley-shape; and putting the welding portions onto the joint surface situated at interval between said pipes; and then welding both of welding portions and the joint surface together to integrate the structure.
As a basic installation aspect, this automobile door reinforcing member is installed between an outer panel and an inner panel of an automobile door, with the joint surface and the outer side faces of pipes toward the outside of an automobile, and at the same time, the longitudinal direction of pipes is in front and back direction of an automobile.
The pipe is formed by folding the fold-back faces of an original sheet having welding portions at the inner wall faces extending from the folded-back faces. By being welded the welding portions and the joint surface are joined integrally to provide sufficient bond-strength of pipes with the joint surface. The welding portions and the joint surface are superposed, thus, a simple, cheap and continuous welding process is applicable such as spot-welding.
To improve the structural strength of a pipe itself, quenching of an intermediate portion of pipe is effective for an automobile door reinforcing member of the present invention. In practice, concerning stress variance put on pipes, the product consists of a beam structure with twin strong supporting pipes with installation parts formed to both ends of a product, and the quenching is performed on an intermediate portion of pipe.
Continuous roll forming can be used for the pipe forming process. Accordingly, an automobile door reinforcing member of the present invention is manufactured efficiently from the original sheet by being supplied continuously in sequential order from a roll forming process to a spot-welding process. Furthermore, at a cutting/separating process, the product is obtained by cutting and separating the tubular article in the product length, which completes the processing continuously after passing through the roll forming process and the spot-welding process. By necessity, the bending process that bends a product according to an automobile door and the quenching process are provided before a cutting/separating process. Despite these bending process and quenching process, productivity is not impaired by reason of the operation of these processes occur while passing through the spot-welding process continuously. The installation parts of a product are obtained after cutting and separating by crushing both ends of pipe. The installation part being formed by crushing pipe has a structure comprising two overlapped original sheets. This makes structural strength higher.
An absorption performance of impact as an automobile door reinforcing member is substantially influenced by shapes of the pipe cross-section. An automobile door reinforcing member of the present invention is formed to be; (1) a pipe consists of an approximately annular cross-section folding the outer side face of the pipe, the outer wall face and the inner side face of the pipe continuously in an arc-shape, (2) a pipe consists of an approximately oval cross-section obtained by bending the outer side face of the pipe and the inner side face of the pipe in an arc-shape, and by extending the outer wall face linearly from the outer side face of the pipe to the inner side face of the pipe, and further (3) a pipe consists of an approximately square cross-section obtained by bending the outer side face of the pipe in an arc-shape, and by extending the outer wall face and the inner side face of the pipe linearly. The cross-section of (1) is a basis of an automobile door reinforcing member of the present invention, and (2) is a cross-section adapting to the thickness of automobile door (a space between the outer panel and the inner panel) by extending the outer wall face. Further, an automobile door reinforcing member of the present invention has a cross-section as (3) to avoid deformation mutually caused by the outer side face of the pipe, the outer wall face and the inner side face of the pipe.
A structure of the joint surface is indented relatively against a form of the outer side face of the pipe. A performance of impact absorption by an automobile door reinforcing member depends on an amount of deformation occurring in the outer side face, the joint surface and the inner side face. If an amount of deformation of the inner side face of pipe is larger than the outer face of pipe, there is some fear of buckling as the impact absorption capacity deteriorates suddenly after a particular point of impact absorption. Therefore, the joint surface is indented relatively against the outer side face of the pipe, then, the central axis line of an automobile door reinforcing member is set toward an inner side face of the pipe. Accordingly, a small gap of an amount of deformation between the outer and the inner side faces of the pipe is achieved by improving the modulus of section of the inner side face of the pipe, then, restraining an amount of deformation of the inner side face of the pipe. A dent of the joint surface is simultaneously formed at the roll forming process serving as bend of the fold-back face. Further, a level difference of a dented joint surface functions as a kind of the rib, and, for example, it restrains generation of strain in said bending process.